An image scanning unit for optically reading an object to be read is mounted in an apparatus that forms an image, such as a scanner or a copier. The image scanning unit includes a light source unit that emits light while moving along a reading surface of the object to be read and a plurality of reflecting members that deflect reflected light from the object to be read to guide the light to an image reading section provided with an image sensor.
In the image scanning unit, the light source unit and a reflected image scanning unit having the reflecting members and image reading section are disposed below a platen glass on which the object to be read is placed or in a casing (carriage frame) that can incorporated inside an ADF (Patent Document 1). The light source unit is disposed at an upper surface side of the carriage frame so as to face the object to be read. The reflected image scanning unit is positioned at a rear surface side of the light source unit and has a first reflecting member that first receives reflected light from the object to be read and a plurality of intermediate reflecting members that deflect reading light received by the first reflecting member a plurality of times so as to guide the reading light to the image reading section. The number and arrangement of the plurality of reflecting members are appropriately determined depending on a shape or a size of the carriage frame and arrangement of the light source unit and image reading section.
The light source unit includes a pair of bar-like light guides extending along a longitudinal direction of the object to be read, a light guide holder that holds the pair of light guides such that they extend parallel to each other, and a pair of light sources (LEDs) disposed so as to face one end portions of the pair of light guides. The light source unit is mounted with the light guide holder incorporated in an upper portion of the carriage frame (Patent Document 2).
In the reflected image scanning unit, the reading light received by the first reflecting member disposed below the light source unit is passed through the other intermediate reflecting members disposed in a space inside the carriage frame, whereby a continuous light path of the reading light toward the image reading section disposed at a bottom portion of the carriage frame is formed.